1.8t Muffler Delete sizes?

Thinking of doing a muffler delete (aka removing the suitcase) to give my car more growl. What size piping should be recommended for our cars when doing this? 2.25, 2.5, or 3?

Well stock is 2.25, so you'll need the part where the clamp connects to the new piping to be that. Then I assume you're referring to after the clamp, which I don't have much of an idea, but I imagine the larger the louder.